1. Field of the Invention
The present invention relates to a semiconductor storage and, more particularly, to a layout of a sense amplifier of a semiconductor storage.
2. Description of the Related Art
A sense amplifier of a semiconductor storage is connected to a pair of bit lines to which a memory cell is connected and it functions to amplify a minute potential difference produced between the paired bit lines as data stored in the memory cell in the form of an amount of electric charges is supplied to the paired bit lines.
An example of the sense amplifier is formed of a first n-type MOS transistor having the drain thereof connected to one of the pair of bit lines and the gate thereof connected to the other of the pair of bit lines, a second n-type MOS transistor having the drain thereof connected to the other of the pair of bit lines and the gate thereof connected to one of the pair of bit lines, a third n-type MOS transistor having the drain thereof connected to the sources of the first and second MOS transistors, a first sense amplifier actuating signal being supplied to the gate thereof, and a ground potential being supplied to the source thereof, a first p-type MOS transistor having the drain thereof connected to one of the pair of bit lines and the gate thereof connected to the other of the pair of bit lines, a second p-type MOS transistor having the drain thereof connected to the other of the pair of bit lines and the gate thereof connected to one of the pair of bit lines, and a third p-type MOS transistor having the drain thereof connected to the sources of the first and second MOS transistors, a second sense amplifier actuating signal being supplied to the gate thereof and a power source potential being supplied to the source thereof.
A typical conventional sense amplifier has been designed such that the first n-type MOS transistor and the second n-type MOS transistor share the same characteristics (e.g. gate length/gate width), and the first p-type MOS transistor and the second p-type MOS transistor share the same characteristics.